Move prompt into external file like this

[mhulse]

https://stackoverflow.com/a/11107564/922323

function prompt_command {
  export PS1=$(~/bin/bash_prompt)
}
export PROMPT_COMMAND=prompt_command

This should allow for better encapsulation of all my prompt stuff, and reduce bugs.

Though, read the comments on that stack issue to make sure this is the right approach.